NASA is now live-streaming views of Earth from space captured by four commercial high-definition video cameras that were installed on the exterior of the International Space Station last month. The project, known as the High Definition Earth Viewing (HDEV) experiment, aims to test how cameras perform in the space environment. You can see the live HD views of Earth from space here:

"The cameras are enclosed in a temperature-specific housing and are exposed to the harsh radiation of space," NASA officials write in an online description of the HDEV experiment. "Analysis of the effect of space on the video quality, over the time HDEV is operational, may help engineers decide which cameras are the best types to use on future missions.

You can follow NASA's stream directly here. If the screen is black, don't worry — the space station is likely just on Earth's night side. (The station completes one orbit every 90 minutes, so you won't have to wait too long for our gorgeous planet to roll into view once again.)

The HDEV gear arrived at the orbiting lab aboard SpaceX's robotic Dragon capsule, which blasted off on its third contracted cargo mission on April 18. (SpaceX holds a $1.6 billion deal with NASA to make 12 such resupply flights.) Astronauts then installed the cameras on the space station, and they became operational on April 30.

HDEV isn't the only Earth-imaging project aboard on the International Space Station.

The Vancouver-based company UrtheCast (pronounced "Earthcast") has two HD cameras on the orbiting lab. One of them, known as Theia, takes pictures with a resolution of 16.5 feet (5 meters), while the other camera records video that can resolve details as small as 3 feet (1 m) across.

These two cameras, which together cost $17 million, were installed by spacewalking cosmonauts in January. UrtheCast released the first images from Theia last month and plans to begin streaming near-realtime views of Earth from orbit soon, bringing lots of viewers to their website.

UrtheCast also aims to sell its imagery to a variety of customers, including government agencies interested in tracking resource use and private companies that want to keep tabs on their operations (and perhaps the operations of their competitors).